Connector terminal having a contact socket assembly for receiving the end of a conductor

ABSTRACT

In order to resiliently clamp the stripped end of a conductor to a connector terminal, the latter is provided with a contact socket assembly in which the clamping setscrew is threadedly supported by a nut held on the socket casing by a resiliently deformable spring band. In the operative position of the contact socket assembly, the nut is spaced from the casing wall and the setscrew clamps down on the conductor end by virtue of the force exerted thereon by the deformed spring band.

United States Patent 1 Marechal 1 June 5, 1973 [54] v CONNECTOR TERMINALHAVING A CONTACT SOCKET ASSEMBLY FOR [56] References Cited HE END OF AUNITED STATES PATENTS [76] Inventor: Gilles Adrien Georges Marechal, 36'fgg'ggg 313;: ggtg g Quai dc Bethune, 75 Paris France [22] Filed: Mar.30, 1972 Primary Examiner-Joseph H. McGlynn 1 pp No 239 714Attorney-Edwin E. Greigg Related U.S. Application Data [57] ABSTRACT[63] Continuation-impart of Ser. No. 166,789, July 28, resiliently RStripped of a 9 1971, abandone ductor to a connector terminal, thelatter is provided with a contact socket assembly in which the clamping30] Foreign Application priority Data setscrew is threadedly supportedby a nut held on the socket casing by a resiliently deformable springband. Aug. 4, 1970 France ..7028749 In the operative position of theContact Socket Mar. 30, 1971 France ..71ll094 sembly the nut is Spacedfrom the casing wall and the setscrew clamps down on the conductor endby virtue [52] U.S. Cl. ..339/272 R, 24/125 N of the force exertedthereon by the deformed Spring [51] Int. Cl. ..H0lr 11/10 band [58]Field of Search ..339/45, 272;

13 Claims, 7 Drawing Figures Patented June 5, 1973 2 Shuts-Shoot lPatented June 5, 1973 2 Shuts-Shoot 2 CONNECTOR TERMINAL HAVING ACONTACT SOCKET ASSEMBLY FOR RECEIVING THE END OF A CONDUCTOR Thisapplication is a Continuation-In-Part of application Ser. No. 166,789,filed July 28, 1971, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to connectorterminals of the type having at least one integral contact socketassembly for receiving the stripped end of a conductor, such as amulti-strand cable.

A number of clamping arrangements have been proposed for fastening thebared end of an electrical wire or cable in a contact socket.

Thus, some known devices utilize a simple setscrew which has anoutwardly projecting head and which is screwed transversely across thebody of the contact socket. Others comprise additional locking andwedging means for the conductor. These arrangements do not resistsatisfactorily to sharp pulls on the conductor and have, among others,the disadvantage of not opposing accidental loosening of the screwespecially under the effect of vibrations.

This is why other arrangements implementing locking by resilientclamping have been perfected.

According to one such arrangement, a resilient member, made for exampleof spring steel, is sandwiched between the conductor and the lower faceof the projecting head of the setscrew. In this arrangement, as soon asthe tightening motion of the setscrew is started, the conductor issubjected to an increasing elastic pressure. Thereafter, the end of thescrew comes into contact with the resilient member and starts a directclamping which continues until the locking of the conductor is achieved.The resilient member then assumes a role analogous to that of aresilient washer and opposes an accidental loosening of the screw. Thisarrangement has a disadvantage common to those already stated: thesetscrew cooperates with a feeding thread in the body of the contactsocket which is generally of brass and which therefore must have asubstantial thickness. This requirement, in turn, increases the weightof a component made of a very expensive material.

tial assembly of four distinct components on the con- Anotherarrangement for resiliently locking and clamping a conductor comprises ascrew crossing freely the casing of the contact socket through anopening. The screw is in engagement with a nut situated on the exteriorof the clamping socket and maintained against the latter by anon-deformable yoke applied to the lateral face of the clamping socketopposite said opening. The yoke has a planar face provided with anaperture for the passage of the screw while a resilient washer isinterposed between the nut and the aid planar face of the yoke. The nutand the screw are made of steel. At the end of the clamping operation,the screw withdraws slightly from the contact socket by compressing theelastic washer against the-planar face of the yoke. This arrangementeliminates the disadvantages previously mentioned, but still has adrawback common to all the known arrangements that is, a total, rigidlocking of the.

tact socket.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention toprovide an improved connector terminal of the aforeoutlined type whichhas relatively few components, is easy to assemble and ensures animproved, resilient contacting relationship between the strands of theconductor and the wall of the contact socket body.-

Briefly stated, according to the invention, the contact socket assemblycomprises a screw freely transversing the socket body through ,a lateralopening provided therein and cooperating with an externally situatednut. The latter is held against the contact socket body by a resilientband, preferably of spring steel, applied against the lateral face ofthe contact socket opposite the opening and against the external face ofthe nut. For the passage of the screw, the resilient band is providedwith an aperture aligned with the base of said nut.

The invention will be better understood, as well as further objects andadvantages become more apparent from the ensuing detailed specificationof several exemplary embodiments taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section of acontact socket assembly according to the invention;

FIG. 2 is an end elevational view of the assembly shown in FIG. 1 takenfrom the right;

FIG. 3 is a perspective view of one component of the same assembly;

FIG. 4 is a longitudinal section of a female terminal incorporating theassembly shown in FIGS. l-3;

FIG. 5 is a view similar to that of FIG. 4, showing the structure in analternate position and FIGS. 6 and 7 are schematic and elevational viewsof two operational positions of a form for preshaping a braidedconductor.

DESCRIPTION OF THE EMBODIMENTS As shown in FIGS. 1-3, an electricterminal 1, here a male plug or jack, has at one end an integral socketbody 2 which forms part of a contact socket assembly and which has anopen-ended axial bore 2a. The latter receives the bared end of anelectrical conductor having twisted strands (not shown).

The socket body 2 comprises an external planar surface portion 3, havinga circular aperture 4 centered on the longitudinal axis of the surfaceportion 3.

The contact socket assembly further comprises a nut 6 which has arectangular base 10 and an external face 12. The latter is cylindricaland has an axis which is parallel to the longer center line of therectangular base 10. The base 10 which is designed to be placed on theplanar surface portion 3 of the socket body 2 comprises at its middleportion, a recess 1 l which, in the example shown, forms a broadtransversal channel. The external face 12 of the nut 6 has at its centera cylindrical protrusion 9 traversed axially by a threaded nut bore.

The nut 6 cooperates with a headless screw 5 designed for clamping theconductor and which, at its extremity inside the axial recess 2a carriesa disc 13 having a slightly convex work face 14. The diameter of thedisc 13 is slightly smaller than that of the circular aperture 4. Thedepth and the width of the channel 1 1 in the nut 6 are such that thedisc 13 may be entirely withdrawn thereinto without protruding beyondthe plane of the base 10. v

The contact socket assembly further includes a strip of rolled springsteel forming a resilient band 7 designed to maintain the nut 6 securelyon the planar surface portion 3 of the socket body 2. The band 7 has anoval cross section and is applied respectively against the lateralsurface of the socket body 2 diametrically opposite the planar surfaceportion 3 and against the external face 12 of the nut 6, at the two endsof the major axis of the oval. The band 7 is provided with an opening toreceive the protrusion 9 of the nut 6. In the emboidment shown, thelast-named opening is provided in the two thicknesses of the band whichoverlap after formation of the closed band. This arrangement provides afixation of the two extremites of the band and avoids the necessity ofjoining the overlapping layers by soldering or the like.

The components of the contact socket are assembled as follows: The screw5 is threaded into the nut 6 from the side of its base until the disc 13entirely nests in the recess 11. Then, the screw-and-nut assembly isintroduced into the band 7 in such a manner that the slot ted end of thescrew 5 and then the projection 9 pass through the opening in the wallof the band 7. Thereupon the latter is inserted onto the socket body 2,while the base 10 of the nut 6 glides on the planar surface portion 3 ofthe socket body 2. A few turns of the screw 5 suffice for the disc 13 toreach or pass through the aperture 4, whereupon the assembly ofcomponents 5, 6, 7 can no longer be separated from the socket body 2.

Subsequent to introducing the end of the electric conductor in the axialbore 2a of the socket body 2, the screw 5 is turned inwardly whichbrings the face 14 of the disc 13 against the conductor. By virtue ofthe engagement between the planar surface portion 3 of the socket body 2and the base 10 of the nut 6, the advancement of the screw is effectedperpendicularly to the axis of the socket bore 2a. As soon as theresistance of the conductor to the advancement of the screw reaches acertain magnitude, a further tightening of the screw 5 will cause amovement of the nut 6 away from the socket body 2, resulting in adeformation of the resilient band 7. Thus, the major axis of the band 7increases, its minor axis decreases, while side portions 7a, 7b (FIG. 2)tend to assume a flat shape. It is apparent that the elastic resistanceof the band 7 increases proportionally with its deformation and that itmay be calculated to reach a greater value than that of the force of thescrew before the deformation becomes maximum, that is, before the sideportions 7a and 7b become actually planar. Thus, an extremely forcefulclamping is obtained which, nevertheless, still remains resilient.Consequently, a completely rigid locking of the conductor will notoccur.

It is to be noted that the convex form of the work face 14 of the screw5 enhances its penetration into the conductor. Thus, the convex face 14bites into the conductor spreading the strands without harming them andforcefully presses them against the internal surface of the contactsocket assuring an almost individual contact between each strand, on theone hand, and the inner wall of easing 2, on the other hand. For afurther improvement of the electric contact between the connectorterminal and the conductor, the stripped end of the latter may be tinnedand the setscrew 5 with disc 13 annealed or silver-plated.

Turning now to FIGS. 4 and 5, there is shown a female terminal 15adapted to receive a prong or jack 23 of a male terminal 24. Theterminal 15 incorporates a contact socket assembly 19, 31, identical instructure and in operation to the assembly described hereinabove inconnection with FIGS. 1-3. Accordingly, to the terminal 15 there issecured, by means of the contact socket assembly 19, 31 a conductor byits stripped end 20. The socket body 19 has a crimping jaw 16 whichholds one end of a tubular metallic braiding 17 disposed coaxially in ashaft 21 of the terminal base 22. The crimping jaw 16 is annealed andoutwardly flared. The other end of the braiding 17 is affixed to asimilar crimping jaw integral with a contact head 26 provided at its endwith a silver or silverplated rivet 28. In the shaft 21 between thesocket body 19 and the head 26 there is disposed a helicoidal spring 18under compression, urging the contact head 26 into engagement with aninner annular shoulder 27 of the terminal base 22 in the absence of theprong 23. Each strand of the braiding 17 is tinned at least at its end.The diameter of the shaft 21 and the coil spring 18 is so designed as toallow a free ballooning of the braiding-l7 when the head 26 movesinwardly.

After having cut the braiding 17 to the desired length, each of its endsare preshaped. For this purpose, as shown in FIGS. 6 and 7, each end isplaced in a mold 30 having a channel of semicircular bottom and a widthsubstantially equal to the smallest inner diameter of the crimping jaws16, 29. The braiding then takes a substantially oval cross sectionalshape (FIG. 6). A punch 32, the working surface of which is acorresponding semicircular groove, is then lowered (FIG. 7) to give theend of the braiding a circular cross section of small diameter. At thesame time, this operation produces an increase in the thickness of thewall of the tubular braiding. Advantageously the ends of the braidingare then coated with conducting grease to correct any damage that mighthave been caused by the preshaping operation to the tinning of some ofthe strands. The braid ends are then introduced respectively into thecrimping jaws 16 and 29. By virtue of the flared configuration of thejaws 16, 29, the said introduction may be performed with ease.Thereafter, the clamping is effected in a known manner. The clampingjaws are deformed circularly, or preferably hexagonally in order thatthe braiding be in alignment with the contacts.

In order to prevent the possible occurrence of an undesirable voltagedrop due to a faulty annealing of crimping jaws 16, 29 resulting in animperfect electric contact with the braiding 17, each crimping jaw ispunched at diametrically opposite locations to provide clampingdeformations such as indicated at 33 on the crimping jaw 16 and at 34 onthe crimping jaw 29.

A structure as described in connection with FIGS. 4 and 5 improves theparasite contacts which appear in every electric connection andconsequently reduces an ohmic voltage drop and thus the joule-type heateffect. The aforenoted pressure contact-type structure, however, has tobe further improved for currents of more than amperes.

The phenomenon of energy losses in such structure for currents in excessof 60 A is not yet well explained; it is the result of the interactionbetween the conductors forming the braiding 17 and the spring 18 whichprobably gives rise to Foucault currents. The energy losses increasewith the current intensity, with the number of turns of spring 18 andwith the cross section of the spring wire.

It has now been found that, all other parameters being constant, theaforenoted energy losses decrease as the magnetic susceptibility of thespring material is decreased. Accordingly, the invention provides aspring which is made of a metal having the necessary resilientcharacteristics and has, in addition, a very small magneticsusceptibility.

As it may be observed from the Table which follows, the INOX 12 Rnon-magnetic steel yields very satisfactory results. In the tests, inall instances the current intensity was 125 A, the spring 18 had 18turns of a wire of 3.14 mm cross section. The temperatures were taken atthe base of the crimping jaw carried by the head 26.

TABLE Type of the Spring Material (French Standard Designations) VoltageDrop Temperature of Heating No Spring 17.5 mV 41C Electrolytic Copperl8.5 mV 39C INOX 12 R l0 non-magnetic steel 17.5 mV 41C INOX 18/8 2 15CN 18-08 Steel 20 mV 44C XC-70 Spring Steel, isolated from the contacts35 mV 48C XC-70 Spring Steel, not

isolated 36.5 mV 50C The electric contact -has to be established betweenthe head 26 of the female member 22 and the prong 23 with a well definedfirm pressure. The latter should not vary significantly while thecontact is being made so as not to increase to an excessive extent theforce of engagement. Also, in order to maintain the aforenoted voltagedrop at a minimum value, it is essential not to increase the number ofturns in the spring 18. But, in order to ensure that the contactpressure varies only slightly as the contact head 26 moves between itstwo limiting positions, the closer the spring is to its relaxedposition, the greater should be the number of turns. For reconciling theforegoing opposing requirements, and thus to ensure an approximatelyconstant contacting pressure without considerably increasing the numberof turns in the spring 18, the latter is preferably used in the zone ofhalf-compressed state instead of using it in the zone of its relaxedstate. Consequently, even in the absence of the prong 23, significantresidual elastic forces will be present which normally would cause anelongation of the braiding 17, a deterioration of the connection of thebraiding 17 in the crimping jaws and eventually a deterioration of thebraiding itself. For avoiding these harmful effects, the expansion ofthe spring 18 has to be limited. Thus, in accordance with the invention,the shaft 21 terminates in an inwardly extending radial shoulder 27against which as set forth earlier the contact head 26 abuts underspring pressure in the absence of an external counterforce. In thismanner the movement of the contact head 26 and thus the expansion of thespring 18 is outwardly limited. By virtue of this arrangement it iseffectively prevented that at any time the force of the spring istransmitted to the braiding 17. Such an occurrence would cause anundesired elongation of the braiding l7 and a weakening of its crimpedconnections.

What is claimed is:

l. A contact socket assembly for clamping an electric conductor,comprising,

A. an elongated socket body having 1. an axial bore open at least at oneend, 2. a lateral opening,

B. a setscrew freely passing through said opening and having a path oftravel normal to the axis of'said axial bore, said setscrew adapted topress said conductor in said axial bore against said socket body,

C. a nut disposed externally of said socket body and having a threadedbore in alignment with said lateral opening for threadedly engaging andholding said setscrew and D. a resilient band surroundingcircumferentially said socket body and said nut to resiliently urge thelatter into engagement with said socket body.

2. A contact socket assembly as defined in claim 1, wherein saidresilient band is in engagement with that part of said socket body whichis diametrically opposed to said lateral opening.

3. A contact socket assembly as defined in claim 2, wherein said nut hasa curved external surface to conform to the curvature of that portion ofsaid resilient band that is in engagement with said nut.

4. A contact socket assembly as defined in claim 3, wherein saidresilient band has the shape of an oval.

5. A contact socket assembly as defined in claim 1, wherein said nutincludes an outwardly extending annular projection surrounding anopening of said threaded bore, said band is provided with an aperturethrough which said projection passes.

6. A contact socket assembly as defined in claim 1, wherein the externalface of said socket body is provided with a planar surface portionsurrounding said lateral opening, said last-named portion serving as anengagement face for said nut.

7. A contact socket assembly as defined in claim 1, wherein saidsetscrew carries, on its end oriented towards said axial bore, a dischaving an outer work face for engaging said conductor in said axialbore.

8. A contact socket assembly as defined in claim 7,

I said axial bore.

11. A contact socket assembly as defined in claim 1, extended by aclamping terminal in order to form a terminal designed to assure theconnection between a flexible conductor inserted in the crimpingterminal and the end of a cable introduced into the socket characterizedin that the internal surface of the crimping terminal and each of thestrands of the flexible conductor, at least in the neighborhood of itsextremity, are protected by tinning and/or silver-plating; the saidcrimping terminal is annealed and presents a flared shape; the end ofthe flexible conductor being preshaped before mounting; said crimpingterminal having two diametrically opposed stamping marks or clampingdeformations.

12. A contact socket assembly as defined in claim 11, including amovable contact head, a braiding constituting said flexible conductor,said braiding having one end secured to said contact socket assembly andanother end secured to said contact head, a coil spring surrounding saidbraiding and urging said contact head away from said contact socketassembly, said coil spring being made of a material of small magneticsusceptibility.

13. A contact socket assembly as defined in claim l2,

in a direction away from said contact socket assembly.

1. A contact socket assembly for clamping an electric conductor,comprising, A. an elongated socket body having
 1. an axial bore open atleast at one end,
 2. a lateral opening, B. a setscrew freely passingthrough said opening and having a path of travel normal to the axis ofsaid axial bore, said setscrew adapted to press said conductor in saidaxial bore against said socket body, C. a nut disposed externally ofsaid socket body and having a threaded bore in alignment with saidlateral opening for threadedly engaging and holding said setscrew and D.a resilient band surrounding circumferentially said socket body and saidnut to resiliently urge the latter into engagement with said socketbody.
 2. A contact socket assembly as defined in claim 1, wherein saidresilient band is in engagement with that part of said socket body whichis diametrically opposed to said lateral opening.
 2. a lateral opening,B. a setscrew freely passing through said opening and having a path oftravel normal to the axis of said axial bore, said setscrew adapted topress said conductor in said axial bore against said socket body, C. anut disposed externally of said socket body and having a threaded borein alignment with said lateral opening for threadedly engaging andholding said setscrew and D. a resilient band surroundingcircumferentially said socket body and said nut to resiliently urge thelatter into engagement with said socket body.
 3. A contact socketassembly as defined in claim 2, wherein said nut has a curved externalsurface to conform to the curvature of that portion of said resilientband that is in engagement with said nut.
 4. A contact socket assemblyas defined in claim 3, wherein said resilient band has the shape of anoval.
 5. A contact socket assembly as defined in claim 1, wherein saidnut includes an outwardly extending annular projection surrounding anopening of said threaded bore, said band is provided with an aperturethrough which said projection passes.
 6. A contact socket assembly asdefined in claim 1, wherein the external face of said socket body isprovided with a planar surface portion surrounding said lateral opening,said last-named portion serving as an engagement face for said nut.
 7. Acontact socket assembly as defined in claim 1, wherein said setscrewcarries, on its end oriented towards said axial bore, a disc having anouter work face for engaging said conductor in said axial bore.
 8. Acontact socket asSembly as defined in claim 7, wherein said work facehas an outwardly convex configuration.
 9. A contact socket assembly asdefined in claim 7, wherein the diameter of said disc is slightly lessthan that of said lateral opening.
 10. A contact socket assembly asdefined in claim 9, wherein that face of said nut which is orientedtowards said socket body is provided with a recess to receive said discwhen said setscrew is fully withdrawn from said axial bore.
 11. Acontact socket assembly as defined in claim 1, extended by a clampingterminal in order to form a terminal designed to assure the connectionbetween a flexible conductor inserted in the crimping terminal and theend of a cable introduced into the socket characterized in that theinternal surface of the crimping terminal and each of the strands of theflexible conductor, at least in the neighborhood of its extremity, areprotected by tinning and/or silver-plating; the said crimping terminalis annealed and presents a flared shape; the end of the flexibleconductor being preshaped before mounting; said crimping terminal havingtwo diametrically opposed stamping marks or clamping deformations.
 12. Acontact socket assembly as defined in claim 11, including a movablecontact head, a braiding constituting said flexible conductor, saidbraiding having one end secured to said contact socket assembly andanother end secured to said contact head, a coil spring surrounding saidbraiding and urging said contact head away from said contact socketassembly, said coil spring being made of a material of small magneticsusceptibility.
 13. A contact socket assembly as defined in claim 12,including means defining a shaft accommodating said coil spring, saidbraiding and said contact head, a shoulder disposed in said shaft and inthe path of travel of said contact head, said coil spring urging saidcontact head into engagement with said shoulder in the absence ofexternal forces opposing said coil spring, said shoulder limiting thedisplacement of said contact head in a direction away from said contactsocket assembly.